This invention relates to a forceps for extracting stones in the pelvis of a kidney.
FIG. 1 shows a typical known forceps 1 for extracting stones in the pelvis of a kidney. The forceps 1 comprises a pair of shanks 3 pivotally connected to each other at an intermediate point. Each shank 3 has a stone-clamping portion 2 at one end and a finger ring 4 at the other end. In one of the finger rings 4 a thumb is inserted, and a forefinger into the other finger ring 4. The forward portion of each shank 3, which includes the stone-clamping portion 2, is curved to deviate from a plane in which the finger rings 4 are moved toward or away from each other. The forward portions of the shanks 3 are inserted into the pelvis of a kidney to the depth shown by the line A--A so that a stone, if any in the pelvis, may be clamped between the clamping portions 2 when the finger rings 4 are moved toward each other and the stone thus may be extracted from the pelvis.
Since it is not known where a stone is located in the pelvis, it would be difficult to bring the stone-clamping portions 2 to clamp the stone therebetween when the forceps 1 is inserted for the first time. In most cases the stone-clamping portions 2 must be repeatedly inserted into the pelvis until they are brought to a position to clamp the stone. Usually it takes a long time to extract the stone out of the pelvis, thus inevitably keeping the patient in pain for a long time. Sometimes, the stone fails to be removed.
To ascertain where a stone exists in the pelvis, X-rays are applied on the pelvis of the kidney. When, however, the stone and the kidney wall have nearly equal X-ray permeabilities, making it impossible to find the stone in the pelvis, the stone must be caught by the stone-clamping portions 2 by a trial and error method.
FIG. 2 shows another known forceps for extracting stones in the pelvis of a kidney, which is provided with a telescope. The forceps comprises a tube 5 bent at an intermediate portion, a pair of jaws 6 provided at the distal end of the tube 5, and a pair of shanks 7 provided at the proximal end of the tube 5. The shanks 7 are pivotally connected to each other at their one end and each have a finger ring at the other end. An operation wire 9 extends through a wire guide tube 8 which extends along the tube 5. The wire 9 is connected at one end to said one end of one of the shanks 7 and at the other end to the proximal end of one of the jaws 6. When the finger rings of the shanks 7 are moved toward each other with the fingers, the wire 9 is pulled to close the jaws 6.
Also extending through the tube 5 is a telescope 10. Through the telescope 10 a stone, if any, in the pelvis of a kidney can been seen. While seeing the stone through the telescope 10, the operator manipulates the shanks 7 thereby to clamp the stone between the jaws 6. Thus it is easy for the operator to find and clamp the stone. However, since the wire 9 fails to transmit the delicate movement of the shanks 7 to the jaws 6, the jaws 6 cannot clamp the stone as readily as the operator wishes to. Another problem with the forceps of FIG. 2 is that the size of the stone in the pelvis cannot be known through the telescope. Thus, even if the jaws 6 successfully clamp the stone, the stone cannot be extracted if it is too large.